Engine balancing



I Dec. 15,1942. I J. DlCKON 2,304,392

ENGINE BALANCING Origihai Fi1 ed June 5. 19:59 3 Sheets-Sheet i oimQz'cksozz MOMENT 4800 T CENTER OF ENG/NE /4.4'A50V (RANKJf/AFT Q Dec.15,.1942.

J. plcksoN I ENGINE BALANCING Original Filed June; 5, 1939 3Sheets-Sheet 2 0910 lgp (5 (RANK ANGLE 000/ens fimalvx 9:. CliioinetfDec. 15, 1942. J. DICKSON ENGINE BALANCING 3 Sheets-Sheet 3 OriginalFiled June 5, 1939.

i gmlenio'b I 2 01222 z'c'kson a $61, I W I atio msgb Patented Dec. 15,1942 umraosmrss PATENT OFF ENGINE BALANCING John Dickson, Ferndale,Mich., assignor to General Motors Corporation, Detroit, Mich., acorporation of Delaware Original application June 5, 1939, Serial No.277,423. Divided and this application January 23, 1942, Serial No.427,901

2 Claims.

then in an opposite direction at the frequency of the speed of thecrankshaft, or at higher harmonics of that speed.

It is well known that in a single cylinder engine, any harmonic of theinertia forces of the reciprocatin masses may be balanced, by a pair ofeccentric masses revolving in opposite direc tions with the samefrequency as the inertia force to be balanced, together balancing theinertia forces, and counter-balancing each other in a direction at rightangles to the direction of the inertia forces; and that in amulti-cylinder engine, a harmonic couple due to the inertia forces ofthe reciprocating masses and tending to rock the engine in the plane ofthe cylinder center lines may be balanced by a pair of eccentric massesat each side of the neutral axis, revolving at the frequency of theparticular harmonic to be balanced, and oppositely phased from eachother to give the required balancing couple. In cases where the numberof cylinders is such that there is more than one rocking couple of thesame harmonic, the balancing masses for the the aggregative side thrustforces of all the pispistons on each side of the neutral axis have beenaggregated in a single pair of eccentric masses producing the requiredbalancing couple for each of the inherent rocking couples at therequired time.

It is also known that in a single cylinder engine, a harmonic couple dueto the piston side thrust forces and their corresponding reactions atthe crankshaft, and tending to rock the engine in a plane normal to thecrankshaft axis, may be balanced by an oppositely alternating coupleproduced by a pair of eccentric masses revolving at the frequency of theparticular harmonic to be balanced, and so phased and spaced from eachother to produce the required counteracting couple in said plane. Sinceit is not usually possible or convenient to arrange the required massesactually in the plane of the connecting rod they are divided on eitherside thereof.

In a multi-cylinder engine, while any harmonic couple of the side thrustforces of each of the pistons and their reactions at the crankshaft inplanes normal to the crankshaft axis may be independently balanced inthe same way, such a construction would be expensive if it is nototherwise impracticable. It has heretofore been proposed to aggregatethe requisite balancing masses for the couples of a certain harmonic at'each crank, in a single pair of masses in the plane of symmetry of theengine, or divided between pairs of eccentric masses at each end of theengine, and'to combine with such masses the requisite masses forbalancing the inertia forces of the same harmonic, but in all instancesonly the couples and forces of those harmonics of a frequency equal tothe speed of the engine multiplied by the number of differently phasedcranks have been balanced, and then only in those cases where the crankarrangement has been such that tons produce no aggregative couples ofthe same harmonic tending to twist the frame of the engine in a plane orplanes parallel to the crankshaft axis and normal to the plane of thecylinder center lines, and the inertia forces produce no couple tendingto rock the engine in the plane of the cylinder center lines. This isprobably so, for the reasonthat the couples at each crank in planesnormal to the crankshaft axis are differently phased even thoughidentical, and it has been believed that since a single pair of massescan only produce two opposite forces and one reversing couple perrevolution, they must run at'the enginespeed multiplied by the number ofdiiferentlyphased cranks, or some whole multiple thereof, to balance thepiston side thrust couples and inertia forces at all the cranks, andthen are only suitable for balancing the couples of a harmonic frequencyequal to that speed; and cannot, while producing equal counteractingcouples for the couples at all the cranks, at the same time producedifferent balancing couples for the difierent side thrust force couplesof pistons spaced diiferent distances from a neutral axis, in a plane orplanes parallel to the both the inertia forces'in the plane of thecylinder center lines and the piston side thrust couples in planesnormal to the crankshaft axis of that harmonic of engine speed equal tothe number bend the engine frame.

longitudinally of the engine has not heretofore been known.

Now if the piston side thrust forces of a multicylinder engine areconsidered as a whole in a plane or planes parallel to the crankshaftaxis and normal to the plane of the cylinder center 7 lines, andindependently of their reactions at the crankshaft, they may produce anagg'regative' couple or couples in such planes parallel to thecrankshaft axis, varying periodically in value at some multiple ofengine speed, and tending to If the piston side thrust forces do as awhole produce an aggregative couple in a plane or planes parallel to thecrankshaft axis and normal to the plane of the cylinder will-produce asimilar but opposite aggregative couple in that planeof the crankshaftaxis normal to the plane of the cylinder center lines, thus tending tobend the engine frame in an opposite direction. V

The couples due to the piston side thrust forces acting in one directionand those due to their reactions at the crankshaft acting in an oppositedirection, in parallel planesspaced from each other, are frame twistingcouples and hereafter will be so designated.

' is plotted against crank angle theiresultin'g curve may be used todetermine the equations for each harmonic of the piston side thrust inone cylin- .der in terms of the crank angle); assuming the sameequivalent piston side thrust force at the V V same crank angle in eachcylinder, these forces ,l are multiplied by their respective distancesfrom y la neutral axis at the center of the engine, to W cylinder centerlines, at the aforesaid mean dis- 3 tance from the crankshaft axis; themoments of the piston 'sidethrust forces in each cylinder" center lines,their reactions at the crankshaft in this plane are then tabulated intheir proper phase relationship relative to the various crank angles forone of the cylinders, andsummed to give for allthe various crankshaftpositionafthe total or resultant maximum moment in a plane the plane ofthe cylinder centerlines, at the aforesaid mean' distance fromrthecrankshaft axis. Y

In order to find'the sum, or the resultant'of F-the moments of aparticularharmonic of the All two cycle multi-cylinder in line or V type5 engineswith cranks arranged for firing at'equal intervals once perrevolution in each cylinder have rocking couples of one harmonic or morein planes longitudinally of the engine, and this invention is concernedwith the balancingof any such harmonic frame twisting couple or couples(in a plane normal to the plane of the cylinder center lines) in suchengines or any other engines in which frame twistingcouples exist, in asimple and practical way, by-masses aggregated-at the ends of theengine.

One object of the invention is a method and means of balancing frametwisting couples of any harmonic, resulting from the piston side thrustforces in a multi-cylinder engine;

' mum engine speed and load, as resolved in a plane parallel to thecrankshaft axis and normal to the plane of the cylinder center lines ata mean distance from the crankshaft axis.

The mass of the reciprocating parts being known, and an indicator cardbeing available, the piston side thrust forces in one cylinder, due togas pressure andinertia force, at equal crank angle intervals throughoutone cycle are determined and tabulated together with their respectivemoments about the crankshaft axis; the sum of the moments is divided bythe sum of the forces, to obtain the mean distance from the crankshaftaxis at whichthe piston side thrust may be considered to occur; then bydividing the moments at the various crank angles by the mean distance,the equivalent side thrust force at this distance from the crankshaftaxis, at the various crank angles during one revolution is determined;(when this piston side thrust force axis and normal to the cylindercenter lines :at.j theaforesaid mean distance from the crankshaft pistonside thrust forces of all the cylinders in:

the same mean plane, in terms of that harmonic of the engine (assumingthe distance between adjacent cylinders to be unity), to ,obtain theirrelative moments; these momentvectors are then summed vectorially inorder to determine the V resultant moment vector, its relative size andits phase angle for all the cylinders combined; the

actual resultant moment is of course the product,

of the resultant moment vector, the cylinder spacing in inches, and theexpression for the same harmonic of the piston side thrust force in onecylinder, with the necessary change in the term which is a functionofthe crank angle,

because of a change in the phase angle for all the cylinders combined.The resulting, equation gives for all the various crankshaft positions,the

total or resultant moment of the particular har; 1 jmonic of the pistonside thrustforcesof all the cylinders in a plane paralleltoithecrankshaft axis.

According to the invention, the resultant maximum rocking couple of anyharmonic of the pis- "tonside thrust forces of all the cylinders, ina

plane parallel to the crankshaft axis and normal to the cylinder centerlines and the opposite reaction couple in that plane of the crankshaftaxis normal to the plane of the cylinder center lines are resolved intoalternating oppositely phased duced by at least one pair ofgeccentricmasses constituting weights geared to the engine crank shaft andrevolved thereby in each of said planes at the speed of the harmonic tobe balanced, about axes spaced from each other on the engine frame. Inorder to produce the required balancing couples in planes normal to thecrankshaft center lines. If, however, they revolve in unlike or oppositedirections -their axes must lie in spaced planes normal to .the plane ofthe cylinder center lines for the reason that if they were to revolve inopposite directions about axes in a common plane normal to the plane ofthe cylinder center'lines they could only produce an alternating forceand no alternating couple in the plane normal to the crankshaft axis inwhich they revolve. When they revolve in opposite directions about axesin spaced planes normal to the plane of the cylinder center lines theyproduce both an alternating couple and an alternating force in the planenormal to the crankshaft axis in which they revolve. If, in thesecircumstances, the mass and moment of the weights is such that theoppositely alternating forces at each end of the engine will balance aninertia force couple'in a Well known way, the distance apart of saidplanes of their axes may be made such that the alternating couples theyproduce will balance the couples to be balanced in the planes normal tothe crankshaft axis in which they revolve. A train of gears at each endof the engine in which there are gears running in the same direction andin opposite directions, i. e., at least three gears, is, however,desirable, particularly where'both inertia force couples and frametwisting couples are to be balanced if only for the reason that theindividual gears may then. be located in any position best suiting thedesign requirements of the engine, (i. e., the gears necessary to drivean overhead camshaft may be positioned without regard to their use forbalancing the engine). Should the disposition of the balancing masses onsuch gears give rise to an unwanted couple about an axis displaced fromthe plane of the cylinder center lines, it may be balanced by theaddition of small auxiliary balance masses in two of the gears such thatthey will create an opposing couple at the required instant.

Because the piston side thrust couples change almost directly as thecylinder mean effective pressure changes, and the effectiveness of therotating eccentric masses changes as the square of the speed at whichthey are rotating, complete balance will only be achieved at the speedand mean effective pressure for which the balance weight's' weredesigned; for all "other speedsand mean effective pressures thesummation of the pistonsidethrust couples willbe somewhat over or underbalanced.

The primary and secondary frame twisting couples aregenerally large inmagnitude compared with the summation of all the harmonics, and theframe deflecting effect of the various harmonics diminishes as thesquare of the harmonic producing it, so that by counteracting the firstand perhaps the second harmonic, the total frame twisting couple isreduced to-a negligible fraction of its original value. Accordingly, itwill seldom be necessary in practice to balance more than the primaryand secondary harmonic couples, althoughany' higher harmonics can bebalanced in a similar way, .provi'ded'th'e gear train includes, gearsrunning at the frequency of the particular harmonic.

The force required of the eccentric balance weights in planes normal tothe crankshaft axis at each end of the engine, to balance the frametwisting couple of a particular harmonic of the piston side thrustforces of all the cylinders, is obtainedby dividing the couple-{by thedistance betweenthe weights at opposite ends of the engine;themass-radius or moment of aneccentric weight which produce :an:equiv-alent scentrifugal force when-running :atthe speed of theparticularharmonic is thendetermined; eccentrio weights of a similarmass. radius, but oppo- 1 sitely phased, are also required at each endof the. engine, to balance the reaction of the frame twisting couple inthe plane of the crankshaft.

Since "the two alternating fram twisting couples in 'planes'parallel tothe crankshaft axis are oppositely phased, their eccentric balancingmasses at'each end of the engine will each create second.moment-couplesin their planes normal to the crankshaft axis. 'It willbe apparent therefore that the axes of the eccentric balancing masses ateach end of the engine need .notbe both in the plane .of the cylindercenter lines and in the-planes of their .respective Jframe twistingcouples, but that provided their couples in planes normal to thecrankshaft axis remain unchanged,

and equal to the couples to be balanced, the

Figure 1 is a diagrammatic perspective view of l the crankshaft of avertical four-cylinder in-line, two-cycle engine, with gears running atengine speed in gear trains: at each end of the crankshaft.

Figure 2 is a diagrammatic view of the rear gear train as viewedfrom'the front on line 2--2 of Figure l, with the addition to the gearwheels of the requisite eccentric masses for balancing the rockingcouples due to the primary inertia forces.

Figure 3 is a diagrammatic View of the rear gear train as viewed'fromthe front on line 22 of Figurel' with the addition to the gearwheels of the requisite'eccentric masses for balancing the firstharmonics of the primary fram twisting couples.

Figure 4 is similar to Figures 2 and 3, bu shows the required balancingmasses of Figures 2 and B'superimposed' upon one another in their properphase relationship'to produce the several required moments occurring atvarious angles of some of the gears.

Figure 5 shows the balancing masses of Figure 4 resolved into singlemasses in their respective gears, as applied to each end of the engineof Figure 1, with the'required moments in particular angularrelationships to each other and the crankshaft, to completely balancethe first harmonic of the frame twisting couple and the primaryinertiarocking couple, at full load.

Figure 6 shows an alternative disposition of balancing masses in amodified gear train at the front end of an engine similar to that shownin Figure 1, cooperative with the balancing masses in the gear train atthe rear end of the engine, to completely balance the same couples asthose dealt with in the arrangement of Figure 5.

Figure 7 shows Various moments, at a mean distance away from thecrankshaft axis in a plane parallel to the crankshaft axis, and normalto the plane of the cylinder center lines, of an actual two cycle enginehaving a cylinder and crank arrangement as shown in Figures 1, 5, and

Figure 8 shows a possible gear train for balancing avertical two-cycleengine having primary inertia couples,' secondary inertia couples, and

secondary frame 'twisting couples.

Figure 9 shows 'a possible gear train for bal ancing afour-cylinder'two-cycle 45 V engine having a primary inertia rockingcouple, a primary frame twisting couple, secondary inertia forces, and asecondary torque reaction couple. I The vertical four-cylinder in-linetwo-cycle engine of Figures 1, 5 and 6 has four cranks I, 2, 3

and amammmas; Cranks and 4 are at 180 to each other and cranks :2 and 3are at 180 to each other in aplane at right angles to the plane ofcranks and 4 for power impulses to the cranks in the sequence 1, 3, 4, 2every 90 of crankshaft rotation. The crank arrangement is such thatthere is a rocking couple due to the primary inertia forces and aprimary frame twista ing couple due to the piston side thrust forces.

In Figures 1, 5, and 6 there is atthe rear end of the engine, a train ofgears all of which run at. engine. speed, consisting'of a gear wheel. H)

on theprankshaft, a crankshaft idler gear II, a:

respectively at the opposite end of the;eng ine.

In Figure 2, which shows eccentric balancing weights A,'B, and C, havingthe requisite momerits forbalancing the primary inertia rocking couple,the eccentric weights A and C are similarly'ph'ased on the gears l2 andH) which run in the same direction; while the weight B is oppositelyphased on the gear I running in' an opposite-direction. The moment ofthe weights A,'B and C,*as represented by their-reference characters, issuch that A+B+C is equal to the moment of a revolving weight whosecentrifugal force is sufficient to balance the'force of the primaryinertia rocking couple; and AB+C=0. The weights D and E areequal andoppositely phased'onthe'gears 2 and H], to balance the v unwanted couplearising about the line of the plane of the cylinder center lines, due tothe fact that the axes of the weights A and B are displaced from theplane of the cylinder center lines: Their moments as-represented bytheir reference. characters are such that (Axm')'+(D y)=(B 'z)- and Ay)' (D x)=(B w) 7 It willbe seen that the weights A, B and C are sophased that theywill create an alternating upward and downward forcewhich will at all times balance the force of'the couple due to theprimary inertia forces in the plane of the cylinder center lines. a

In Figure 3, which shows eccentric balancing weights having therequisite moments for balancing the primary frame twisting couples dueto the piston side thrust forces, the 'eccentric weights F and G areequal .but oppositely phased on the gears I2 and H! respectively, whichrun in the same direction. The weights I and J are similarly equal andoppositely phased on the gears l2 and I3, and are required in order toprovide a couple which will balance the unwanted couple arising aboutthe line of the plane of the cylinder center lines (due to the fact thatthe axisof the weight F is displaced from the plane of the cylindercenter lines), and which is ence characters, theirmoments are such that(Fxm)+(I y) is equal to'the product of'the moment of a revolving weightwhose centrifugal force is sufficient to balance the force of r theframe twisting couples, and the distancebetween the planes of the frametwisting'couples; o'r-exthe crankshaft 'axis, which will have itsmaximum value when the resultant moment of the primary I forces is a Vharmonic of the piston side thrust maximum.

In Figure 4, the Weights. A, 13,0, 1), and E or V Figure 2, and F, G,Land J of Figure 3, have been superimposed upon one another in their 5proper phase relationship. The resultant mo:

' ment of all the masses'in each of the gearsis then determined, andFigure 5 shows the resultants K, L, M in their proper phaserelationship, with similar weights N, O, P in the gears 22, 2| and 20,but oppositely phased from those in the gears I2, H and I0.

Figure 6 shows an alternative dispositionlof' I the balance 'weights forthe primary inertia couples and the primary frame twisting couples x inthree gears 30, 3| and 32 atthe front end of the engine, of which thegears 3| and 32 have their axes in a plane normal to theplane of thecylinder center lines and are spacedfrom a third gear 30 onthecrankshaft axis. The. gear 3l is" on the camshaft M, and runs in anopposite "directionfrom the crankshaft gear 30,. while the gears 33 and32 run in the same direction. The

and 32, with auxiliary masses in the gears 39 and 3|, because gears 3|and 32, are at unequal dis- 'tances from the plane of the cylindercenterlines.

each of The resultants R, S, T of the masses in the gears are disposedas shown. In Figure 7, in which the moments piston side thrust forces14.4" above the crankshaft center line, are plotted against differentpositions of the'crankshaft withreference to the crank angle of crankthe curve #1 shows the sum or the resultant maximum moment of the frametwisting couples of all harmonics of the 7 piston side thrust forces at.maximum engine speed; the curve #2 shows the firstharmonic of curve #1;the curve #3 shows the moment produced by the balance gears. which isequal but opposite to that produced'by the piston side thrust forcesshownyin curve 2; the curve #4 shows the unbalanced moment; left in theengine,

after the first harmonic of the piston side thrust force couples hasbeen balanced.

The engine of the arrangement shown in Fig ure 8, is assumed to be onein which the pri mary frame twisting couple is so small as to require nobalancing, but in which there is a primary inertia rocking couple, asecondaryinertia rocking couple, and a secondary frametwisting couple tobe balanced. The balancing masses for the primary inertia coupleare'divided be-' tween threegears 40, 4| and "at one end of aboutthecenter of an actual enginesuch as that shown in Figures 1, 5, and 6, inthe mean plane of the the engine, and 50, iii and 52 at the opposite endof the engine, and running at engine speed. The gears M and i run in anopposite direction to the gears 40, 42 and 5t, 52. The axes of thesegears in each train are in the plane of the cylinder center lines, sothat when the weights A, B and C and the corresponding but oppositelyphased weights D, E, F at the opposite end of the engine, which have amoment distribution in the ratio one, two, one, are in a horizontalposition, there will be no unbalanced moments in either of the geartrains. In their vertical position the weights are phased alike, andtheir moments at each end of the engine are additive to create therequisite forces to balance the primary inertia rocking couples. Thesmall gears 43, to run in opposite directions at twice engine speedalong with their corresponding gears 53 and 54 at the opposite end ofthe engine. The balance weights G and I in their horizontal position areoppositely phased in the gears 43 and M, and the balance weights J and Kin the gears '53 and 5d are similarly phased opposite to each other andto the weights G and I. It will be seen that in their vertical positionbecause of their rotation in contrary directions, the weights G and Iare phased alike, and that the weights J and K in their verticalposition are phased alike but in an opposite direction to the weights Gand I. The weights G, I and J, K, are therefore additive to balance thesecondary inertia rocking couple. So that they may at the same timebalance the secondary frame twisting couple, their distance apart I),can be made such that the moments required of the weights G, I, and J,K, to balance the secondary inertia rocking couple will produce atwisting couple of a magnitude which will balance the secondary frametwisting couple.

The engine of the arrangement shown in Figure 9 has two camshafts 51 and58 (one for each bank of cylinders), geared together to run in oppositedirections at engine speed, and driven from the crankshaft 59; a gear61] on the crankshaft, drives, through gears Si, 62 and 63 running attwice engine speed, the gear {ill on the camshaft 58, which is geared tothe gear 65 on the camshaft 51. At the opposite end of the engine a gearH! on the crankshaft, drives gears H, l2 and I3, coaxial with the gearsBI, 62 and 63. Considering the train of gears through which thecamshafts are driven, the requisite masses for balancing the primaryinertia rocking couple are divided between the gears 60, 64, and 65, andthe requisite masses for balancing the primary frame twisting couplesare provided in the gears 60 and 64; the weights L, M, N, are theresultants of all the masses in the gears til, 64, and 65, respectively,which along with the corresponding but oppositely phased weights 0', P,Q, at the opposite end of the engine will balance both the primaryinertia rocking couple and the primary frame twisting couples. Theweights R, S, T, in the gears 6!, 62, and 53 along with thecorresponding and similarly phased weights U, V, W, at the opposite endof the engine provide the requisite masses to balance the secondaryinertia forces and a secondary torque reaction couple.

I claim:

1. In a multi-cylinder engine with a frame, a bank of cylinders in line;pistons in the cylinders, and a crankshaft with a crank arrangement suchthat there are resultant frame twisting couples in spaced planesparallel to the crankshaft axis and normal to the plane of the cylindercenter lines, and a resultant inertia force couple in a plane parallelto the crank shaft axis and the plane of the cylinder center lines, anarrangement for balancing any harmonic of said frame twisting couplesand said inertia force couple comprising means for producing alternatingoppositely phased couples and forces in planes at opposite ends of theengine and normal to the crankshaft axis, said means including at leasttwo revolving eccentric weights in each of said planes at opposite endsof the engine, said weights being driven from the engine crankshaft inopposite directions at the speed of the harmonic to be balanced andabout axes on opposite sides of the plane of the cylinder center linesand in spaced planes parallel to the crankshaft axis and normal to theplane of the cylinder center lines and said two weights at each end ofthe engine including component masses of suitable mass and moment phasedoppositely to each other as seen in positions of revolution in whichtheir directions of eccentricity are normal to the plane of the cylindercenter lines and so phased relatively to the crankshaft as to produceforces in said planes of rotation equal but opposite in phase andopposite to the forces of the resultant inertia force couple in saidplanes of rotation, and the distance apart of said spaced planesparallel to the crankshaft axis and normal to the plane of the cylindercenter lines being such that said component masses produce couples insaid lanes of rotation equal but opposite to the frame twisting couplesto be balanced in said planes.

2. In a multi-cylinder engine with a frame, a bank of cylinders in line,pistons in the cylinders and a crankshaft with a crank arrangement ofthe kind described, such that there is a resultant inertia force couplein a plane parallel to the crankshaft axis and the plane of the cylindercenter lines, and resultant frame twisting couples which can be resolvedinto a couple in a plane normal to the crankshaft at one end of theengine and an oppositely phased couple in a similar plane at theopposite end of the engine, an arrangement for balancing any harmonic ofsuch a resultant inertia force couple and resultant frame twistingcouples including a pair of revolving eccentric weights of suitable massand moment in each of said planes at opposite ends of the engine, saidweights of each pair being driven from the engine crankshaft in oppositedirections at the speed of the harmonic to be balanced and about axes onopposite sides of the plane of the cylinder center lines and in spacedplanes parallel to the crankshaft axis and normal to the plane of thecylinder center lines, said weights of each pair being phased oppositelyto each other as seen in positions of revolution in which theirdirections of eccentricity are normal to the plane of the cylindercenter lines and so phased relatively to the crankshaft as to produceforces in-said planes of rotation equal but opposite in phase andopposite to the forces of the resultant inertia force couple in saidplanes of rotation, and the distance apart of said spaced planesparallel to-the crankshaft axis and normal to the plane of the cylindercenter lines being such that said weights produce couples in said planesof rotation equal but opposite to the frame twisting couples to bebalanced in said planes.

JOHN DICKSQN.

